Updating the careers section

Steps

1. Create a new branch.
2. Navigate to content/openings folder.
3. Create a markdown file with its name as the title of the job in lowercase.
4. Add a url where the job post is listed and the proper title of the job inside the markdown file created in the previous step.

---
title: Front-end Engineer
url: https://angel.co/company/civicdatalab/jobs/1279092-front-end-engineer
---

5. Create a pull request with the changes.